The present invention relates to a knit-in slide fastener in which a fastener tape thereof is composed of a warp knitting structure and a continuous fastener element row formed of thermoplastic-synthetic-resin-made monofilament is fixed along a fastener element mounting portion on a longitudinal side edge of the fastener tape simultaneously with knitting of the fastener tape. More particularly, it relates to a knit-in slide fastener which makes it possible to stabilize pitches between the fastener elements by forming a knitting structure of the fastener element mounting portion to be dense and to prevent any cutoff of composition yarns in the fastener element mounting portion due to a sewing needle when end portions of the fastener element rows are fixed.
For example, Japanese Patent Application Laid-Open No.8-314 has disclosed a knit-in slide fastener in which a continuous fastener element row is knitted in and fixed in the fastener element mounting portion formed along a longitudinal side edge of the tape at the same time when the fastener tape is knitted. In the knit-in slide fastener disclosed in the publication, another chain-stitch knitting yarn is knitted into a group of needle loops formed of chain-stitch knitting yarns in the fastener element row which composes a row of wale on the side of a fastener tape main portion such that it overlaps, so that the density of the knitting pattern of a foundation structure in the fastener element mounting portion is made large with the chain knitting formed in duplication, thereby stabilizing the mounting of the fastener element row.
Such technology for stabilizing the mounting of the fastener element row is also disclosed in for example, Japanese Patent Application Laid-Open No.11-187909. According to this publication, all yarns composing the fastener element mounting portion are provided with a higher heat shrinkage property than the yarns which compose the fastener tape main portion. Then after knitting, the composition yarns are subjected to heat treatment so as to allow the yarns in the fastener element mounting portion to shrink more than the composition yarns in the fastener tape main portion. Consequently, the fastener element mounting portion is formed to be dense so that its dimension can be stabilized, and the fastener element row is tightened firmly with the fixing chain-stitch knitting yarns in order to secure a high engagement strength.
In the fastener element mounting portion of the knit-in slide fastener disclosed in the above-described publication, any of the fixing knitting yarns for fixing the fastener element row onto the fastener tape is composed of ordinary long fiber yarns made of synthetic resin in order to secure a fixing strength.
The knit-in slide fastener disclosed in the publication restricts an operating end of a slider by providing both end portions thereof with an upper stopper and a lower stopper, in the same manner as an ordinary slide fastener. Because each of these upper and lower stoppers is usually composed of small pieces made of metallic material or synthetic resin material, their mounting portions of the stoppers are protruded outward when such a slide fastener is sewed to trousers or a skirt, so that its appearance is not good. Particularly, in the case of an upper stopper, which is mounted in a separate manner to the right and left, it is difficult to fit the slider to the same upper stopper, so that a fastener portion between the slider and the upper stopper is separated during use, thereby causing an inconvenience in appearance.
On the other hand, because the knit-in slide fastener, which the present invention aims at, is excellent in flexibility as compared to the woven fabric type slide fastener in terms of the structure, it has been often employed for particularly flexible clothes. However, if the slide fastener is attached with stoppers as mentioned above, the inconvenience becomes remarkable. For this reason, conventionally end portions of the fastener element rows of the fastener chain were sewed directly to an object such as clothes by a sewing needle, without attaching the stoppers.
When the fastener element row is being attached to clothes or the like by sewing the end portions thereof directly with a sewing needle, the sewing needle crosses over the end portions of the fastener element row for sewing. Then, the sewing needle may be pierced into the fixing knitting yarns existing at the fastener element mounting portion of the fastener tape located between the respective fastener elements or the other composition yarns existing at the mounting portion, so that the yarns pierced by the sewing needle can be cut down. Therefore, when the slide fastener is being opened or closed, or when mechanical operation is applied upon washing, the yarns of the fastener element mounting portion get frayed, or part of the fastener element row may be removed from the fastener tape.
If heat treatment such as thermal setting is carried out after the fastener stringer is manufactured, likewise the knit-in slide fastener which the present invention aims at, hardness and tension of the yarn itself are heightened. Therefore, the yarns tend to be cut off easily due to interference with the aforementioned sewing needle. Particularly, if a small-diameter yarn which is very flexible is used, the yarn is more likely to be cut off.
The present invention has been achieved to solve the above described problems, and a concrete object of the invention is to provide a knit-in slide fastener in which when end portions of a fastener element row are mounted directly to clothes by sewing, any of the yarns that compose the fastener element mounting portion of the fastener tape is never cut off due to an interference with a sewing needle, so that the yarns of the fastener element mounting portion are prevented from being frayed, thereby ensuring an excellent durability.
The above-described object can be achieved by a basic structure of the present invention, that is, a knit-in slide fastener comprising a continuous fastener element row, which is knitted therein simultaneously with knitting of a warp-knit fastener tape, at a fastener element mounting portion on a longitudinal side edge portion of the warp-knit fastener tape, said fastener element mounting portion being composed of a fixing knitting yarn for sandwiching and fixing upper and lower leg portions of each of the fastener elements from front and rear sides thereof and other knitting yarns, characterized in that said fixing knitting yarn is a textured yarn.
That is, according to the present invention, a textured yarn is employed for the fixing knitting yarn of the fastener element which is part of the composition yarns of the fastener element mounting portion. The textured yarn mentioned here refers to a processed yarn obtained by executing crimp processing for crimping fibers by means of deforming a number of long fibers obtained from spinning of synthetic resin material and thermally set them, and then applying air eddy to the crimped yarns so as to entangle the yarns with each other in a complicated style at every predetermined interval.
According to an experiment by the inventors of the present invention, it has been verified that the textured yarns can ensure as sufficient a fixing strength as the fixing knitting yarn composed of an ordinary long fiber yarn, so that it can be used for practical purpose from the viewpoints of the strength.
By the way, the fastener element mounting portion is formed continuously along the fastener tape main portion. The knitting structure thereof applies knitting yarns for connecting the fixing knitting yarns with stitches, or various kinds of in-laid yarns to be inserted through the stitches of the fixing knitting yarns, other than the fixing knitting yarns for the fastener element row. The typical knitting structure of the fixing knitting yarns include chain stitches, tricot stitches, two needle stitches and the like. These knitting structures are knitted independently or in combination. The various kinds of the in-laid yarns may include a warp in-laid yarn which is inserted while being entangled with sinker loops on a wale, a weft in-laid yarn which is inserted in between the sinker loops and needle loops over a multiplicity of wales.
Generally, if the chain knitting pattern is adopted as the fixing knitting yarn, two knitting yarns of the needle loop stride over the upper leg portion of an element while a single knitting yarn of its sinker loop is disposed so as to intersect the lower leg portion, so that the upper and lower leg portions are sandwiched and fixed. Thus, its tightening force is extremely stronger than the other fixing knitting pattern structure. Further, because the stretching in the direction of the wale (longitudinal direction of the fastener tape) is less due to the structure of the knitting pattern. Therefore, in the case where it is intended to knit the fastener elements into the fastener tape by adopting the structure for the fixing knitting yarn, the fixing of the fastener element is stabilized, which is particularly preferable.
However, originally, not only this chain knitting structure is less stretched in the direction of the wale as described above, but also if this is adopted for the fastener element fixing structure, a larger tension is produced in the chain-stitch knitting yarn after having been knitted than in an ordinary knitting yarn, so that a strong tension is applied thereto. Under this condition, when an element portion at the end portion of the fastener element row of the fastener stringer is attached to clothes by sewing, the yarn which is most likely to interfere with a sewing needle and be cut off thereby among the composition yarns of the fastener element mounting portion is often the aforementioned fixing knitting yarn which is exposed on the surface of the fastener elements and is being tightly stretched.
According to the present invention, the textured yarn having the above described structure as this fixing knitting yarn is used. Thus, when an end portion of the fastener element row of the fastener stringer with no end stop is attached to clothes by sewing, even if the sewing needle interferes with the strongly stretched fastener element fixing knitting yarn so that a tip of the sewing needle is pierced into that knitting yarn, a number of crimped fibers which compose each fixing knitting yarn are warped laterally and stretched only locally. As a result, the sewing needle can pass through between a number of the fibers, so that it never cuts off an entire part of the yarn. Further, even if the sewing needle is pierced into one of the composition fibers of the fixing knitting yarn and then cut off the fiber, no fraying occurs in the fibers because the cut off fiber is entangled with the other composition fibers in a complicated style at every predetermined interval.
According to the present invention, it is preferable that the fixing knitting yarn includes a chain-stitch knitting yarn and this fixing chain-stitch knitting yarn is a textured yarn, as mentioned above. Further, as already described, since a chain-stitch knitting yarn, which is most excellent in fixing strength, is employed as the fixing knitting yarn, the fixing strength to the fastener elements is also secured by the knitting structure.
Furthermore, it is preferable that a dry heat shrinkage ratio of the textured yarn is in a range of 6 to 10%. Further preferably, of composition yarns of the fastener element mounting portion, the dry heat shrinkage ratio of the knitting yarns other than the fixing knitting yarn is in a range of 12 to 15%. Still further, the dry heat shrinkage ratio of the composition yarns of the fastener tape main portion other than the fastener element mounting portion in the fastener tape is in a range of 6 to 8%.
Generally, in this kind of the slide fastener, as disclosed in Japanese Patent Application Laid-Open No. 11-187909, it is preferable to provide all the yarns which compose the fastener element mounting portion with the same dry heat shrinkage ratio because a strong tension is increased in the fixing knitting yarn coupled with the foundation structure, which strides over the upper leg portion of the fastener element, by heat treatment after having been knitted. On the other hand, in order to secure a dimensional stability of the fastener stringer and a predetermined mounting strength of the fastener element, it is preferable to set the dry heat shrinkage of all the composition yarns in the fastener element mounting portion to be higher than the dry heat shrinkage ratio of the composition yarns in the fastener tape main portion of the fastener tape.
However, in the conventional knit-in slide fasteners, the dry heat shrinkage ratio of the fixing knitting yarn is set lower than the dry heat shrinkage ratio of the other composition yarns in the fastener element mounting portion.
The reason is that the strength of each fiber is lower and likely to be cut off because the aforementioned fixing knitting yarn is a bundle of a number of fine fibers so that no unreasonable tension force is to be given. Further, the fixing knitting yarn having such a low shrinkage ratio can secure a total strength required for the fixing knitting yarn because the strength can be increased when each composition fiber is stretched.
Further, a dimensional stability of the fastener stringer and a fixing strength necessary for the fastener element row can be obtained by setting the dry heat shrinkage ratio of the composition yarns other than the fixing knitting yarn in the fastener element mounting portion to be high and by setting the dry heat shrinkage ratio of the fastener tape main portion of the fastener tape to be substantially as low as the fixing knitting yarn.